WordNet (r) 3.0 (2006):

character set
    n 1: an ordered list of characters that are used together in
         writing or printing

The Free On-line Dictionary of Computing (30 December 2018):

character set

    A particular mapping between characters and
   byte strings, i.e. the combination of a particular
   character encoding (which maps between byte strings and
   integers) and a particular coded character set (which maps
   between integers and characters).

   For example: ASCII (the ASCII coded character set, encoded
   directly as single-byte values), or UTF-8 (the Unicode
   coded character set, encoded with an 8-bit transformation
   method).

   The character repertoire is the complete set of all
   characters in the character set.

   (2015-11-29)